Thread Mic and Internal Threading

[gun410]

I was referring to the PVC sch 40 PLASTIC pipe. I am sure you could get some practice with the black pipe but its not nearly as forgiving which to me is very helpful when in "Learning" mode.

I see, i guess my local home depot does have it.

You should level your lathe, period. I would suggest doubling or tripling the thickness of your current top, laminating the wood so you have a solid base. It needs to be inset inside the lip on top of the chest if there is a raised lip. Get it solid, then level the lathe on top of that. Even if you move the base cabinet it shouldn't alter the lathe level too much. Get it level, get the tailstock aligned, or you will not be able to do precision work.

This bar that you linked to is the one I use but his may have grinding marks on it. I would ask him to send you pics of the two he has on sale so you can decide if you want it. He started out with 9 of these exact bars, seems like he has sold 7 of them. The advantage to this bar is that it uses either 0.007" or 0.002" nose radius flat top inserts with positive axial rake. Of course, you have to wait until they show up on ebay or pay retail but this is an awesome geometry. The other thing to do is to be patient and wait; another will show up eventually. The hard thing is that since I published that boring article, you are now competing with all the other guys!

As for the other bars, read the article I wrote and think about the geometry a bit and then make your choice. I certainly cannot choose for you. You might also start a thread and ask the guys. I know the SCLCR boring bars are popular because there are a ton of cheap bars sold in sets. The guys will be able to tell you how well they work.

If your drill bit is small, it is flexible, especially a jobber drill. A screw machine drill of the same diameter will be shorter and, consequently, stiffer.

Well if I'm going to level my lathe I'm tempted to weld up a steel bench for it but i'm open to changing the tool cabinet but i would have to take the rollers off. right now i have 2 1/4" steel plates sitting under the lathe and the wood top. I could buy a sheet of 3/4" plywood and screw down 2 layers of that to the wood top.

I offered $50 on that bar and he countered at $55 but I haven't accepted yet because i would rather have a longer bar than 4". I would rather get a carbide boring bar that takes ccmt inserts, i can only find CDCD 51 with a .015 nose radius.

I also have to buy a tool that will work for turning the outside of the baffles (60 deg). The picture is from Ecco Machine, but my parting tools sucks in this lathe, it wont even cut straight with a locked caraige. I'm not sure what tool what be best for this any suggestions?

 

[mikey]

Okay, you have two 1/4" thick steel plates with one layer of 3/4" ply on top of that to which the lathe is mounted? If so, then that is enough. I would not change the cabinet. I would just level the lathe on top of that stack and it should be solid enough. Even if the cabinet moves a bit, it won't be able to warp two layers of plate steel bolted to a plywood top. I suggest you find a way to use leveling devices that attach to the steel through the wood, though. One of our guys did a nice job on his; I'll try to find his thread.

Your call on the boring bar. The problem I have with CCMT/CCGT inserts is that the smallest nose radius I am aware of is the 21.50 insert, which has a 0.008" nose radius. This is okay for general work but you cannot get down to 0.002-0.004" so you have to really know how to work with that larger nose radius. You can do it; I just personally prefer a smaller nose radius. The CM CCBI can use a 0.002" NR but you have to either wait for it to come up on ebay or buy it retail and they are not that cheap. Still worth it in my experience but its your money so you have to decide.

As for the parting tool, I can tell you that inserted carbide works but cutting forces are higher. I much prefer HSS. In my experience, loose gibs or crappy tolerances in the carriage/compound assembly is responsible for most parting issues. You might consider making a solid plinth for your lathe; that will resolve most parting issues for you.

 

[mikey]

Here is the thread by @TerryH that I was referring to.

 

[gun410]

Okay, you have two 1/4" thick steel plates with one layer of 3/4" ply on top of that to which the lathe is mounted? If so, then that is enough. I would not change the cabinet. I would just level the lathe on top of that stack and it should be solid enough. Even if the cabinet moves a bit, it won't be able to warp two layers of plate steel bolted to a plywood top. I suggest you find a way to use leveling devices that attach to the steel through the wood, though. One of our guys did a nice job on his; I'll try to find his thread.

Your call on the boring bar. The problem I have with CCMT/CCGT inserts is that the smallest nose radius I am aware of is the 21.50 insert, which has a 0.008" nose radius. This is okay for general work but you cannot get down to 0.002-0.004" so you have to really know how to work with that larger nose radius. You can do it; I just personally prefer a smaller nose radius. The CM CCBI can use a 0.002" NR but you have to either wait for it to come up on ebay or buy it retail and they are not that cheap. Still worth it in my experience but its your money so you have to decide.

As for the parting tool, I can tell you that inserted carbide works but cutting forces are higher. I much prefer HSS. In my experience, loose gibs or crappy tolerances in the carriage/compound assembly is responsible for most parting issues. You might consider making a solid plinth for your lathe; that will resolve most parting issues for you.

I have 1 10"x10"x1/4" plate under each leg of the lathe, The wood top isn't super thick so I'm considering screwing 2 more layers of 3/4" plywood on top. Terry's way was cool, but i would rather swap the rollers for leveling feet so i know the lathe can't move around and it stays level.

I would prefer a boring bar with CDCD insert so i have the ability to use a .002" NR. The only thing preventing me from buying that 4" boring bar is the length of it, I would prefer a 6" oal bar, and the availability of the inserts. When i order a boring bar I want to be able to use it right away, but i'm a little confused on inserts. I went through ebay and found the only CDCD inserts, but I got quite confused with all the different variety and I don't know how to tell the insert's NR. There is CDCD-500, CDCD-15, CDCD-51 will they all work in that boring bar?
CDCD-500 .002 NR CDCD-15-CM2 CDCD-02-CM2 CDCD-15-CS2
If i can't find the right inserts for the CCBI-250 bar i'll probably buy a micro 100 bar so I can start turning as soon as i get it.

I have tried hss parting before and it worked ok on aluminum but i wouldn't cut 17-4 so i switched to carbide but when you advance the carbide parting tool and pressure on the part increases the tool shifts to the left (returns straight after cutting) not producing an even cut. The right side of the cut doesn't end up being square and the cut shifts to the left the deeper you go. It could be the gibs since i haven't done much with them, but i doubt it. So that why I asked for a suggestion for an alternative tool to profile the outside of the baffles.

 

[mikey]

Correct me if I'm wrong, please. Are you under the impression that leveling the tool cabinet is somehow related to the leveling of the independently mounted lathe on top?

As for the CCBI boring bar, a 6" bar is nice but a 4" bar is adequate. Consider that the max extension of a 1/4" bar is only 2.5", which leaves you with 1.5" in the holder. You need 3-4 times the OD to hold a bar securely so at a minimum you need 1" to hold that bar. In addition, the vast majority of the time you will not be boring at max extension. Your call but my 1/4" and 3/16" CCBI bars are both 4" long and work fine.

The CDCD500 insert has a 0.002" NR. A CDCD505 insert has a 0.007" NR. A CDCD15 insert has a 0.015" NR; no bueno.

With regard to the parting tool, consider that a carbide insert is damned stiff. It takes a fair amount of pressure to bend an insert and typically a carbide insert will break before it bends much. Is it possible/likely that the structure of the lathe is moving? And why are you having to exert so much feed pressure? Are you absolutely positive your tool is on center? If you are, how are you setting that height - by eye? When a parting tool requires a great deal of feed pressure, it is almost always the case that it is set too high; the tool is contacting the work below the cutting edge. If tool height is correct, is it possible that there is enough slack in your carriage/compound to allow upward travel? This needs to be sorted.

We are getting way off topic (threading and thread mics) and it appears that your questions are not being viewed because they are buried in this thread. Might be better to start another thread regarding your choices for boring bars and perhaps another on lathe leveling and another on parting tools. The reason for suggesting this is so you have the entire forum weighing in on answering your questions. I'm sure there are many other guys who own a lathe like yours that would be able to give you better answers. Something to think about, maybe?

 

[gun410]

Correct me if I'm wrong, please. Are you under the impression that leveling the tool cabinet is somehow related to the leveling of the independently mounted lathe on top?

As for the CCBI boring bar, a 6" bar is nice but a 4" bar is adequate. Consider that the max extension of a 1/4" bar is only 2.5", which leaves you with 1.5" in the holder. You need 3-4 times the OD to hold a bar securely so at a minimum you need 1" to hold that bar. In addition, the vast majority of the time you will not be boring at max extension. Your call but my 1/4" and 3/16" CCBI bars are both 4" long and work fine.

The CDCD500 insert has a 0.002" NR. A CDCD505 insert has a 0.007" NR. A CDCD15 insert has a 0.015" NR; no bueno.

With regard to the parting tool, consider that a carbide insert is damned stiff. It takes a fair amount of pressure to bend an insert and typically a carbide insert will break before it bends much. Is it possible/likely that the structure of the lathe is moving? And why are you having to exert so much feed pressure? Are you absolutely positive your tool is on center? If you are, how are you setting that height - by eye? When a parting tool requires a great deal of feed pressure, it is almost always the case that it is set too high; the tool is contacting the work below the cutting edge. If tool height is correct, is it possible that there is enough slack in your carriage/compound to allow upward travel? This needs to be sorted.

We are getting way off topic (threading and thread mics) and it appears that your questions are not being viewed because they are buried in this thread. Might be better to start another thread regarding your choices for boring bars and perhaps another on lathe leveling and another on parting tools. The reason for suggesting this is so you have the entire forum weighing in on answering your questions. I'm sure there are many other guys who own a lathe like yours that would be able to give you better answers. Something to think about, maybe?

Well my plan is to level the lathe by adjusting leveling feet (4-6) underneath the tool cabinet.

I ordered the 4” holder and the cdcd-500 .002 NR. I probably make a holder for it and get an Aloris axa-4d.

Yea it’s not the carbide bending something with the carriage, could it be the gibs?

I will make another thread but I will be doing some threading that I will post here. And I also received my dro so I can tell how deep I’m threading.

Sent from my iPhone using Tapatalk

 

[mikey]

Well my plan is to level the lathe by adjusting leveling feet (4-6) underneath the tool cabinet.

I ordered the 4” holder and the cdcd-500 .002 NR. I probably make a holder for it and get an Aloris axa-4d.

Yea it’s not the carbide bending something with the carriage, could it be the gibs?

I will make another thread but I will be doing some threading that I will post here. And I also received my dro so I can tell how deep I’m threading.

Let me clarify something that might help. If the lathe is mounted to a cabinet that directly supports the ends of the lathe, like a factory stand, then leveling feet on the cabinet can twist the bed and allow you to use those feet to level the lathe. If, on the other hand, the lathe is mounted to a substrate that is itself mounted on a cabinet then leveling the feet will not significantly alter the substrate the lathe is bolted to. It might have a little effect but not much because the lathe is effectively isolated from the cabinet by the substrate. Typically you level the lathe on the substrate and double check it if you have to re-site the lathe but it usually remains stable.

I think the CCBI -250-4-5R is one of the finest small boring bars made, and the CDCD500 is an excellent flat topped insert that is capable of boring in the tenths. Provided the bar is in good shape, it should serve you well. He mentioned grind marks on the bar and I hope they do not affect function.

Provided your parting tool is truly on center, I am not sure why you are having so much trouble parting. Start a thread so the other G0602 can help.

 

[WarrenP]

I have the GO752, same as the 602 except has adjustable speed. I had problems parting also until I got one of the "T" shaped parting tools. after that it works very well. You might try one of those and make sure the tool holder , etc is very ridgid.

 

[gun410]

Let me clarify something that might help. If the lathe is mounted to a cabinet that directly supports the ends of the lathe, like a factory stand, then leveling feet on the cabinet can twist the bed and allow you to use those feet to level the lathe. If, on the other hand, the lathe is mounted to a substrate that is itself mounted on a cabinet then leveling the feet will not significantly alter the substrate the lathe is bolted to. It might have a little effect but not much because the lathe is effectively isolated from the cabinet by the substrate. Typically you level the lathe on the substrate and double check it if you have to re-site the lathe but it usually remains stable.

I think the CCBI -250-4-5R is one of the finest small boring bars made, and the CDCD500 is an excellent flat topped insert that is capable of boring in the tenths. Provided the bar is in good shape, it should serve you well. He mentioned grind marks on the bar and I hope they do not affect function.

Provided your parting tool is truly on center, I am not sure why you are having so much trouble parting. Start a thread so the other G0602 can help.

I haven’t got around to starting a g0602 thread for parting, but the next time I part I will take a good video of the tool shifting and start the thread.

I like the idea of mounting the lathe on the substrate, but either way I don’t have a machinist level. They are pretty expensive $150+ so it might be couples week till I get it. I hope the lathe isn’t being effected by a bad level.

The boring bar worked pretty well, I was running 300 rpms and hand feeding it by feel until I hit the desired depth on the dro. It took a while machining .01 DOC to get the .385” hole to 1.24” diameter. but it was pleasant cutting with the ccbi bar.

The order I’m making these baffles is: boreing hole, profiling inside of cone, profiling outside of cone and parting off. The next step is to bore the inside of the cone with a boring bar or the 1” 60° countersink 1 flute. I will probably use the countersink for ease but I don’t know how to measure how deep to cut with the countersink.

This baffle is going to one of the 2 first blast baffles ( .006” thick vs normal baffle .004” thick). And the overall height of my bb’s is 1.25” and my metal stock only has 1.2” sticking out, can I losses the 3 jaw and pull it out a little or would that screw up concentricity too much?

 

[mikey]

The boring bar worked pretty well, I was running 300 rpms and hand feeding it by feel until I hit the desired depth on the dro. It took a while machining .01 DOC to get the .385” hole to 1.24” diameter. but it was pleasant cutting with the ccbi bar.

Okay, cutting speed for 17-4 stainless is roughly 175-300 sfm, so you need to speed up the lathe. RPM = Cutting speed in SFM X 3.82 / D, where D = diameter of the work piece. So, say your work piece is 1.5" OD. The calculated speed would be somewhere near 764 rpm; this would be a good starting point for external turning. The problem is that we are not external turning; we're boring. Your boring bar is not seeing that 1.5" OD; it is seeing the size of the bore. So, say you started with that 0.385" hole. This would give us 300 X 3.82 / 0.385" = 2976 rpm. Note that as the bore size increases, rpm drops (EDIT: rpm is supposed to drop) until you reach your 1.24" ID, where lathe speed would be somewhere near 1000 rpm. Not only that but your feed is supposed to change with rpm as well. It gets complicated, and this is the stuff I left out of the boring article because it confuses folks.

So, how do you bore a stupid hole? The way I do it is to start with the starting ID and calculate rpm; in this case our starting rpm would be near 3000. Since my lathe cannot go that fast, I would start at the max speed my lathe can run, which is 2400 rpm. I would manually feed the bar because the hole is shallow, blind and because I can feed at whatever feed rate I need to keep up with the speed to produce coiled chips. As the hole gets larger, I cut my speed down IF I have trouble producing the chips I want. Sometimes in harder materials it can be difficult to keep up with the speed and this will cause poor finishes and inaccuracies in the bore. If this is the case, slow the lathe down a gearing step or two and that will allow you to keep up with your feed.

As I keep saying, the lathe teaches us to respond to the cut and this is one example of that. If you cannot feed fast enough to produce the chips you need, slow down the speed until you can.

One thing you must do when boring to precise depths is to use a carriage stop. Do not rely on a DRO; it is not precise enough. Use a stop. If you do not have a stop, buy or make one but get one and use it. I'm not trying to seem draconic here; not only will a stop improve the accuracy and appearance of your bore; it will prevent you from damaging your bar.

The order I’m making these baffles is: boreing hole, profiling inside of cone, profiling outside of cone and parting off. The next step is to bore the inside of the cone with a boring bar or the 1” 60° countersink 1 flute. I will probably use the countersink for ease but I don’t know how to measure how deep to cut with the countersink.

Not sure how the gun guys do this. Maybe post this in that subforum?[/QUOTE]

This baffle is going to one of the 2 first blast baffles ( .006” thick vs normal baffle .004” thick). And the overall height of my bb’s is 1.25” and my metal stock only has 1.2” sticking out, can I losses the 3 jaw and pull it out a little or would that screw up concentricity too much?

Anytime you loosen the jaws of a 3 jaw chuck you lose your origin. However, if you part off a piece and are pulling out stock to make another piece from a longer piece of material then you'll be fine. The next part will be concentric with the spindle centerline.[/QUOTE]